Release notes for LensKit 2.0.2

The Git changelog and the list of closed tickets and pull requests provide more information on what has happened, including bugs that have been fixed.

This is the second bugfix release in the 2.0 series.

• Fix null pointer exception when scoring for nonexistent users (#issue(363)).

• Fix zombie thread keeping evaluator from terminating (#issue(360)).

• Improve error reporting when eval.groovy is missing (#issue(352)).

• Improve CSVDataSource documentation (#issue(364)).

• Added forUser(long) method to History to make it easy to create empty user histories.

• Resolved inconsistency between docs and code for SparseVector.immutable() (#issue(368)).